Update hit rate calculation in performance metrics for improved accuracy

- Changed the method used to convert hit rate from `as_f` to `to_f64`, ensuring better precision in health score calculations based on cache statistics.

Author: eliasjpr

src/performance/performance_metrics.cr

@@ -701,7 +701,7 @@ module CQL::Performance
 
       # Calculate health score based on cache statistics
       cache_stats = cache.stats
-      hit_rate = cache_stats["hit_rate"]?.try(&.as_f) || 0.0
+      hit_rate = cache_stats["hit_rate"]?.try(&.to_f64) || 0.0
 
       # Base score of 100, penalize for low hit rates
       if hit_rate >= 80.0